<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    <script>
        let arr = [1,2,3,4,5,6,7,8,9]
        let sum = 0
        for(let i = 0;i < arr.length;i++){
            sum += arr[i]
        }
        document.write(`数组的和为${sum}`)
        document.write(`数组的平均值为${sum / arr.length}`)
    </script>
</body>
</html>